Technical Field
The present disclosure relates to a transparent organic light-emitting display (OLED) device, and more particularly to a technique for improving transmittance of a top-emission OLED device including a transparent region and an emissive region.
Description of the Related Art
An organic light-emitting display device (OLED) is capable of producing light in its own and thus does not require an additional light source, unlike liquid crystal device (LCD). Also, an organic light-emitting display device can be produced as a thin, transparent display device using a transparent material. Further, an OLED device has advantages in that it is driven with low voltage to consume less power, and in that it represents vivid colors, has short response time, wide viewing angle and good contrast ratio (CR). For these reasons, an OLED device is currently under development as the next generation display device.
It is very important for securing a transparent OLED device to have high transmittance of the transparent OLED device. A top-emission transparent OLED device includes sub-pixel including an emissive region and a transparent region. Accordingly, in order to achieve high transmittance of the transparent OLED device, it is required to make the transparent region as large as possible.
Specifically, as an approach for achieving high transmittance of a transparent OLED device, it has been considered to reduce the area of a driving region included in an emissive region of a sub-pixel. However, since the driving region in a sub-pixel is designed to be optimized for characteristics of components, if the number and/or size of thin-film transistors or capacitors disposed in the driving region are reduced in order to reduce the area other driving region, the reliability of a transparent OLED device may be decreased.
As another approach, it has been considered to increase the area of a pixel in order to achieve high transmittance of a transparent OLED device. However, the area of a pixel of a transparent OLED device is determined based on the resolution of the transparent OLED device. In particular, for a transparent OLED device having high resolution, the area of a sub-pixel is especially small. Accordingly, the area of a pixel is inherently limited by the resolution of a transparent OLED device, and thus it is practically difficult to increase the area of the pixel to achieve high transmittance.
Incidentally, in a typical top-emission transparent OLED device, sub-pixels disposed next to each other have the emissive region disposed next to each other. However, in a top-emission transparent OLED device having such layout of emissive regions, a gap is required between emissive regions of sub-pixels as a process margin. For example, if a transparent OLED device uses red organic emission layers, green organic emission layers and blue organic emission layers to display images, a process of forming the organic emission layers is carried out using a fine metal mask (FMM) so that they are formed in a regular distance. The process is to avoid the organic emission layers from overlapping one another or to avoid the organic emission layers from being formed at undesirable locations. In addition, if a transparent OLED device uses white organic emission layers and a color filter to display images, a certain distance is required during a process of attaching an upper substrate to a lower substrate. In particular, if emissive regions are disposed in line with one another, a process margin is made on two sides of an emissive region. Accordingly, the area of process margins which can be utilized as neither an emissive region nor a transparent region increases. As a result, the area of the emissive regions and transparent regions in sub-pixels are reduced. That is, if emissive regions are disposed in line and next to one another, the area of transparent regions is reduced due to process margins between emissive regions. Also, the aperture ratio of the transparent regions and the transmittance of a transparent OLED device may be reduced.